1. Field of the Invention
The present invention relates to a digital signal transmission method and a digital signal transmission system as well as a transmitting apparatus forming this system and a recording medium for recording a program applied to this transmission system, which is preferably applicable to a case where audio data is transmitted, for example, according to IEEE (The Institute of Electronics Engineers, Inc.) 1394.
2. Description of the Related Art
An audio equipment as related art has been proposed, in which an audio signal is transmitted in the digital form so that the deterioration of sound quality can effectively be avoided.
Specifically, for example, when an audio signal reproduced by the compact disk player is recorded by means of a minidisk device in this sort of audio equipment, the compact disk player modulates the reproduced digital audio signal according to a clock signal of these digital audio signal for outputting. In contrast, the minidisk device on the receiving side employs the PLL circuit to reproduce a clock signal from the transmitted digital signal and then reproduces the transmitted digital signa with reference to the clock signal. In this way, it is arranged that this sort of audio equipment processes the digital audio signal transmitted in synchronism with a clock signal on the transmitting side, for example, to perform processing of recording and so on.
Incidentally, when the digital audio signal is transmitted in this manner, the receiving side will operate synchronously with the clock signal of transmitted digital audio signal. In this case, for example, the bus line of IEEE 1394 system is employed to connect a plurality of audio equipments and, for example, the digital audio signal reproduced from the disk, etc. of a single audio reproducing equipment is sent out to the bus line. That digital audio signal is received and recorded by a recording equipment connected to the bus line.
When such processing to record the digital audio signal is considered, it is necessary in the past that the reproducing equipment is perfectly synchronous with the recording equipment. It is undesirable that the transmitted digital signal contains jitters, whereas the complete elimination of the jitters is difficult.
Moreover, it is considered that, in order to synchronize the reproducing operation of reproducing equipment with the recording operation of recording equipment, control data regarding the reproducing operation, etc. is transmitted over the bus line to synchronize the two equipments. For example, the bus line of IEEE 1394 system is able to connect two or more equipments with one another. However, if the reproducing unit should receive, e.g. control data from another equipment during the recording operation to stop the reproduction, the recording would be interrupted to result in failure.
The present invention is made in view of the foregoing points and has an object that the digital signal transmission between specific equipments is carried out securely and satisfactorily.
In order to solve such problem, the present invention is arranged so that, when a digital signal destination is caused to receive a predetermined digital signal sent out of a digital signal sender, the digital signal destination may acquire from the digital signal sender, at the request of that destination, data on modes in which the digital signal sender is able to send out the digital signal, and a transmission mode of the digital signal may be caused to be set by a command based on the acquired mode data from the digital signal destination.
By doing in this way, the digital signal transmission from the digital signal sender to the digital signal destination is carried out in the mode selected among previously examined modes, thus enabling the digital signal transmission to be securely performed in the determined mode.
Furthermore, the present invention is arranged so that, when a digital signal destination is caused to receive a predetermined digital signal sent out of a digital signal sender, a flag is added to the digital signal sent out of the digital signal sender, which indicates that a transmission rate is being adjusted based on a command from the digital signal destination.
By doing in this manner, the destination is able to check the transmitted flag, so that the processing to eliminate the jitters by the fine adjustment of the transmission rate and the like will be allowed.